With some applications, such as vehicle coatings, multilayer coatings are applied and formed over the substrates thereof, which typically include metal substrates, such as a steel substrates. In some instances, such as with original equipment automotive coatings, the multilayer coatings include, in sequence from the steel substrate, an electrodeposited corrosion resistant layer (or electrocoat layer), a primer layer, a pigmented basecoat layer, and a clearcoat layer. During use, such as driving, such a multilayer coating can be damaged, such as by debris striking the multilayer coating at high velocity.
Repair of the damaged multilayer coating generally involves: sanding the damaged area at least down to or into the electrocoat layer with a series of sanding substrates (or sandpapers) having sequentially decreasing grit size; cleaning the sanded area with a solvent; applying a refinish primer over the sanded and cleaned area; allowing the applied refinish primer to dry; sanding the dried refinish primer layer; applying a refinish basecoat over the dried and sanded refinish primer layer; applying wet-on-wet a refinish clearcoat over the basecoat layer; and allowing the applied refinish layers to cure at ambient conditions for at least a sufficient amount of time, such as at least 8 hours. Typically, the refinish primer, refinish basecoat, and refinish clearcoat compositions and corresponding applied layers are each curable at ambient conditions. After the applied refinish coating layers have cured, a visually observable defect in the form of a ring sometimes appears along the edge of the area of the original sanding step (in which the damaged area was initially sanded). The visually observable defect typically becomes observable within at least one day, such as from 1 to 14 days after application of the refinish repair layers, and is sometimes referred to a “ringing defect” or an “edge mapping defect.” The formation of ringing defects is believed, in some cases, to be due to the refinish primer.
The occurrence of such ringing defects generally requires that the repaired area be subjected to a subsequent repair sequence as described above, beginning with sanding the repaired area at least down to or into the electrocoat layer. Repeating the repair sequence can result in an undesirable increase in the labor and material costs associated with repairing a damaged multilayer coating.
It would be desirable to develop new primers, such as newly developed refinish primers, that provide reduced, minimal, or no ringing defects when used as part of a multilayer repair of a damaged multilayer coating. It would be further desirable that such newly develop primers provide other properties, such as, but not limited to, hardness, flexibility, and adhesion, that are at least as good as primers that do result in the formation of ringing defects.